Layer winding for electrical apparatus

ABSTRACT

In widing a conductor winding for electrical apparatus on a support, the conductor and an insulated tape of greater width than the conductor are simultaneously wound on the support. The tape is wound with a greater pitch than the pitch of the conductor so that the tape reaches the end of the layer sooner than the conductor. The tape is then wound with zero pitch until the conductor reaches the end of the layer, thus forming edge supports for the winding of twice the thickness of the conductor. The pitch of the tape on the next layer is abruptly increased from zero to a value greater than the pitch of the conductor, and from an intermediate point in the layer at which the conductor overlies the tape, the pitch of the tape is decreased so as to build up a body of insulation layer of greater thickness at the end of the layer.

Zetterlund LAYER WlNDING FOR ELECTRICAL APPARATUS [75] Inventor: Uno Zetterlund, Ludvika, Sweden [73] Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden 22 Filed: Nov.'23,19 7l 21 Appl. No.: 201,356

[30] Foreign Application Priority Data Nov. 23, 1970 Sweden 15807/70 [52] US. Cl. 336/206, 336/209 [51] Int. Cl. H0lj 27/32 [58] Field of Search 336/206, 205, 209; .29/605 [56] References Cited UNITED STATES PATENTS 761,039 5/1904 Fortescue 336/205 1,036,935 8/1912 Underhill 336/206 1,223,947 4/1917 Ferrell 336/206 [451 Jan. 1,- 1974 2,213,093 8/1940 Reese 336/206 Primary Examiner-E. A. Goldberg Attorney-Jennings Bailey, Jr.

[5 7 1 ABSTRACT In widing a conductor winding for electrical apparatus on a support,'the conductor and an insulated tape of greater width than the conductor are simultaneously wound on the support. The tape is wound with a greater pitch than the pitch of the conductor so that the tape reaches the end of the layer sooner than the conductor. The tape is then wound with zero pitch until the conductor reaches the end of the layer, thus forming edge supports for the winding of twice the thickness of the conductor. The pitch of the tape on the next layer is abruptly increased from zero to a value greater than the pitch of the conductor, and

from an intermediate point in the layer at which the conductor overlies the tape, the pitch of the tape is decreased so as to build up .abody of insulation layer of greater thickness at the end of the layer.

2 Claims, 5 Drawing Figures g mm x 0 ,6 l 3 L'll'I-I /4 INVENTOR.

U N 0 Z LUN D LAYER WINDING FOR ELECTRICAL APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to layer windings for electrical apparatus such as transformers, reactors or the like.

2. The Prior Art It is known in the manufacture of layer windings for electrical apparatus, such as transformers, reactors or the like, to provide the insulation between two adjacent layers of the winding, the so-called layer insulation, by winding a tape of insulating material on to the frame at the same time as the conductor. Usually the conductor is on top of the tape and the tape and the conductor have the same pitch so that they are always together. When the tape and the conductor reach the ends'of the winding, the winding must be interrupted so that the insulation can be given an extra insert of insulating material so that the layer insulation will be of uniform thickness throughout. This interruption in the winding process at the ends of each layer involves considerable waste of time and consequently increased working costs.

SUMMARY OF THE INVENTION The present invention relates to a layer winding for electrical apparatus, such as transformers, reactors or the like, the layer insulation being manufactured from tapes of insulating material which are wound on at the same time as the conductor and which are wider than the diameter of the conductor. The invention is characterized in that the pitch of the insulating tape is substantially zero at the ends of the winding, while being greater than the pitch of the conductor along at least a part of the distance between the end of the winding.

The invention avoids the disadvantages mentioned in the introduction, that the winding process must be interrupted at the end of each winding layer to complete the insulation and also for application of an edge support for the winding if a bobbin having a permanent edge support is not used. Furthermore, the variable pitch of the insulating tape makes it possible to adapt the thickness of the layer insulation to the tension between two layers so that the layer insulation is thickest where the tension is highest. The edge support can be made of the .same tape as the layer insulation, but it is also possible to use separate tape for this purpose.

BRIEF DESCRIPTION THE DRAWINGS In the accompanying drawings FIGS. 1 4 show various phases in the application of the invention during manufacture of a layer winding for a transformer, and FIG. shows a modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a part of the bobbin or coil frame 1 on which the winding is arranged. The insulating layer 2 lying nearest the coil frame is formed by a tape 3 of paper or other suitable material. The wire or conductor forming the winding is designated 4. It is shown here as circular in cross-section but may be shaped differently, having square or rectangular cross-section, and is varnished or wrapped around with paper in a known manner to insulate the turns of the winding from each other. In the application of the invention shown here, the tape is wound with constant pitch, greater than the pitch of the conductor. Consequently the tape 3 gets a little ahead of the wire and between the wire 4 and the tape 3 there is a finished section of layer insulation, that is, the insulation lying between the coil frame and one winding layer and between two adjacent winding layers. The paper tapehas been previously coated with transverse strips 5 of dried adhesive which cures during a subsequent drying process. The adhesive is to attach the tapes to each other and attach the wire to the layer insulation.

FIG. 2 shows the appearance of the winding at a later stage. The tape 3 has reached the end of the coil frame. Exactly at the moment when the righthand edge of the tape reaches the righthand edge of the coil frame, the pitch of the tape is reduced to zero. Consequently the tape is wound for a certain time on the same area, thus producing an edge support 6, the righthand edge of which is coplanar with the end surface of the coil frame.

FIG. 3 shows the appearance of the winding at the moment when a complete layer of the wire has been wound on to form a winding layer. The righthand turn of wire abuts against the lefthand edge of the edge support. The pitch of the tape in comparison with that of the wire, and the thickness of the tape are so chosen that the thickness of the tape are so chosen that the height of the edge support is substantially equal to twice the radial extension of the winding wire. If the wire has a circular cross-section, with a diameter d,.as in the present case, then the radial height of the support 6 will be 2d.

During the turn subsequent to the position shown in FIG. 3, the next winding layer starts to be formed. The

wire is placed over the finished layer shown in FIG. 3

and starts to move to the left in FIG. 4. At the same time the pitch of the tape 3 which has been zero during the formation of the support 6, is increased. It can be seen in the drawing that the turn of tape covering the righthand wire turn in the upper layer is moved to the left. Since the tape has a greater pitch than the wire, the next turn of tape will project outside the wire in-the second turn. When the wire then forms the third turn, a part of the tape will be folded down between the turns of wire. For each turn, the proportion of tapefinding its way under the conductor increases and forms the layer insulation. As can be seen from FIG. 4, there is no layer insulation between the layers of wire located furthest to the right. This is of no consequence, however, since the difference in tension between the turns in the two layers is so slight that the wire insulation is more than enough. The further to the left the wire moves, the greater becomes the tension between the layers, but at the same time the layer insulation increases and after a certain number of turns, depending on the pitch of the tape, the layer insulation is complete.

In the embodiment of the invention shown and described the pitch of the tape is constant. According to ers of insulation will be alternately thickest and thinnest at the ends of the winding.

In a variation of the invention, the edge support 6 can be formed in two ways. In the first, the tape is so far ahead of the wire that the tape also forms the edge support, as previously mentioned. in the other, the tape runs parallel to the wire or the pitch of the tape is de- 1 creased so much that the wire has time to catch up with the tape just at the end of the layer. The edge support is then formed by another, thinner tape wound on to the end of the winding with zero pitch a number of turns before the tape 3 and wire 4 reach this end.

If the width of the tape 3 is b, its pitch s and thickness t,,, the thickness t of the layer insulation will be t From this it is clear that the thickness of the layer insulation can be varied by one or more of the three parameters in the righthand side of the equation.

The method according. to the invention thus has the considerable advantage that the winding operation need not be interrupted after each turn to complete the layer insulation. The winding operation can proceed continuously since the tape runs in front of the wire producing the layer insulation and the required edge support.

If the conductor used is in the form of a flat tape the edge support may be omitted since the winding will in any case be sufficiently stable at the ends.

The individial successive turns of the tape cannot be shown in the drawings because they are too thin. Each of the spaces 2 in FIG. 1 represents a plurality of turns of the tape.

I claim:

l. A coil for electrical apparatus, such as transformers, the coil comprising a coil frame and a plurality of layers of a conductor and an insulating tape wound on the frame with the conductor and tape progressing across the frame in successive layers of opposite directions, the tape being wider than the conductor, in which the pitch of the tape is greater than the pitch of the conductor within at least a part of each layer and the pitch of the tape at the beginning of the winding of a layer has a value which decreases gradually along the winding towards the opposite end of the winding layer.

2. A coil according to claim 1, in which the pitch of the tape is zero where the tape has reached the end of the frame after a complete layer, said tape forming an insulating layer between two adjacent conductor layers as long as the pitch of the tape is greater than zero, said' tape forming an edge support at the end of the coil frame when the pitch of the tape is zero, the radial height of such a support being about twice the diameter of the conductor. 

1. A coil for electrical apparatus, such as transformers, the coil comprising a coil frame and a plurality of layers of a conductor and an insulating tape wound on the frame with the conductor and tape progressing across the frame in successive layers of opposite directions, the tape being wider than the conductor, in which the pitch of the tape is greater than the pitch of the conductor within at least a part of each layer and the pitch of the tape at the beginning of the winding of a layer has a value which decreases gradually along the winding towards the opposite end of the winding layer.
 2. A coil according to claim 1, in which the pitch of the tape is zero where the tape has reached the end of the frame after a complete layer, said tape forming an insulating layer between two adjacent conductor layers as long as the pitch of the tape is greater than zero, said tape forming an edge support at the end of the coil frame when the pitch of the tape is zero, the radial height of such a support being about twice the diameter of the conductor. 